The problem isn't that the heading contains a full stop, but colons and semicolons stop the compiler as well.

Minimal Source Text To Reproduce

Chapter 1 - A Beginning:
There is room.

Additional Information

The text 'Chapter 1 - A Beginning' seems to be a heading, but does not occupy the whole of its line of source text, which continues ':' . The rule is that a heading must occupy a whole single line which is the only sentence in its paragraph, so there must be a skipped line above and below, and it must not contain any full stop characters '.', even if they occur in an ellipsis '...' or a number '2.3.13'. (I mention this because sometimes this problem arises when a decimal point is misread as a full stop.)